1. Field of the Invention
The present invention relates to winch devices of international patent classification B66D and more particularly, to a winch brake for power winch, which can effectively prevent accidents and enhance operational safety.
2. Description of the Related Art
A winch is a mechanical device that is used to pull in or let out a cable, thereby lifting or lowering a load. A winch is generally equipped with a brake that is provided between the motor and the speed reducing mechanism to prevent the drum from turning when power is off, ensuring the safety of the use of the winch.
A winch brake is known comprising a driving block rotatable by a motor, a driven block connected to a transmission shaft of a deceleration clutch mechanism, a brake spring set between the driving block and the driven block for allowing contraction or expansion of the coil diameter thereof subject to rotation of the driving block, and a brake drum surrounding the brake spring. When starting the motor to pull in the cable, the brake spring is driven by the driving block to contract, forcing the driven block and the transmission shaft of the deceleration clutch mechanism to rotate, and therefore the cable is wound up to lift the load. On the contrary, if the motor is stopped from rotating the driving block after power failure or power off, the driven block will be reserved by the force from the cable to release the brake spring, enabling the brake spring to expand and to rub against the inside wall of the brake drum. Thus, a winch equipped with a winch brake of this design has an automatic braking function.
However, the automatic braking function of the aforesaid winch brake simply relies upon contact and friction between the outer perimeter of the brake spring and the inner perimeter of the brake drum. The brake force of this design of winch brake is insufficient. After a long use, the brake spring will wear, lowering the security. So, there is still room for improvement.